J. of Chromatogr. A 1218 (37), 6540-6547 (2011). New approach and application of highly automated planar chromatographic tools for powerful clean-up, called high-throughput planar solid phase extraction (HTpSPE), which is indispensable for preventing matrix effects in multi-residue analysis of pesticides in food by liquid and gas chromatography coupled to mass spectrometry, employing TLC to completely separate pesticides from matrix compounds and to focus them into a sharp zone, followed by extraction of the target zone by the TLC-MS interface, thus resulting in extracts nearly free of interference and free of matrix effects, as shown for seven chemically representative pesticides in four different matrices (apples, cucumbers, red grapes, tomatoes), and completion of clean-up of one sample in a manner of minutes. Regarding the clean-up step, quantification by LC–MS with mean recovery (against solvent standards) of 90–104% and relative standard deviations of 0.3–4.1% (n = 5) for two spiking levels of 0.1 and 0.5 mg/kg.

J. Chem. Pharm Res. 2(5), 92-96 (2010). TLC of ofloxacin and cefixime on silica gel with methanol - ethyl acetate - 25 % ammonia 7:7:3. The hRf value of ofloxacin was 61 and of cefixime 78. The method was linear in the range of 50-500 ng/band. The recovery was in the range of 99.3-102.2 %. Quantitative determination by densitometry in absorbance mode at 295 nm.

Asian Journal of Chemistry 23(5), 2011-2013 (2011). Methods are reported for determination of organophosphorus pesticides using TLC-cholinesterase inhibition as well as GC-FID. The powdered rice sample was initially extracted with ethyl acetate. The extract was cleaned up by GPC, eluted with cyclohexane - ethyl acetate 1:1, evaporated, and taken up in acetone. This extract was analysed by TLC on silica gel with ethyl acetate to a developing distance of 10-12 cm. After development the plate was air dried, exposed to bromine vapors, sprayed with enzyme solution and incubated at 37 °C for 30 min and sprayed with the reagent. White spots appeared against bluish-red background. The sample was also analysed by GC and the GC method was very sensitive. However, the TLC method is recommended for preliminary screening of samples.

J. Planar Chromatogr. 24, 99-104 (2011). TLC of candesartan and losartan on silica gel with 1,4-dioxane - hexane - 99 % formic acid 50:50:1. Quantitative determination by densitometry at 258 nm for candesartan and at 243 nm for losartan, videoscanning at 254 nm for both drugs. The hRf value for candesartan was 47 and for losartan 35. Linearity was between 0.2 and 1.4 µg/band for both drugs with correlation coefficients of 0.9997 and 0.9981 for candesartan, and 0.9986 and 0.9982 for losartan, for densitometry and videoscanning, respectively. Robustness (%RSD, peak area) was less than 1.9 and 0.8 % for candesartan, and 2.2 and 0.9 % for losartan in densitometry and videoscanning, respectively. The repeatability and intermediate precision (%RSD, two lowest amounts) were less than 3.6 and 4.7 % for candesartan and less than 4.7 and 5.3 % for losartan. Mean recoveries for candesartan were 103.8-104.9 % for densitometry and 99.2-100.7 % for videoscanning; for losartan the respective values were 100.8-105.4 % and 98.6-99.2 %.

J. Planar Chromatogr. 24, 35-39 (2011). HPTLC of olmesartan medoxomil (OLM) and hydrochlorothiazide (HTZ) on silica gel with chloroform - methanol - formic acid 16:3:1 in a chamber saturated for 1 h. Detection under UV light at 254 nm. Quantitative determination by densitometry at 260 nm for olmesartan medoxomil and 272 nm for hydrochlorothiazide. Linearity was between 0.05-1 mg/mL. Average recovery was 100.3 % and 99.9 % for OLM and HTZ, respectively. The LOD was 138 and 137 ng/zone for OLM and HTZ, respectively, and the LOQ was 459 and 456 ng/zone for OLM and HTZ, respectively. The intra-day and inter-day precision (%RSD, n = 9) was 1.2 and 1.4 % for OLM and 1.1 and 1.3 % for HTZ.

J. AOAC Int. 94, 1094-1099 (2011). TLC of caffeine and paracetamol in capsules and tablets on silica gel with n-hexane - ethyl acetate - ethanol 25:15:4. Detection at 254 nm. Quantitative determination by densitometry at 254 and 270 nm. The hRf value of caffeine and paracetamol was 48 and 73, respectively. Linearity was between 0.2-1.9 for caffeine and 0.03-1.5 µg/L for paracetamol. The detection limit of caffeine was 25 ng/L and of paracetamol 32 ng/L. The precision was 1.9 % (n=6). Recovery (by standard addition) was 98-99.5 % for both compounds.

J. Planar Chromatogr. 23, 369-372 (2010). HPTLC of venlafaxine hydrochloride on silica gel with concentration zone, prewashed with methanol, with toluene - methanol 17:7 in a twin-trough chamber saturated for 10 min at 25 +/- 2 °C. Quantitative determination by absorbance measurement at 228 nm. The hRf value was 19. The validated calibration range was 400-2000 ng/band (r = 0.999). Recovery was 98.8-100.3 %. The intra-day precision as %RSD was 0.3-0.6 % and the inter-day precision 0.1-0.3 %. The LOD and LOQ were 97 ng and 294 ng, respectively.

J. of Practical Pharmacy & Clinic 14(2), 134-135 (2011). TLC of estrogenic hormones illegally added to traditional Chinese medicines on silica gel with chloroform - n-hexane - acetone 10:9:2. The hRf values of estrone, stilbestrol, ethinylestradiol, and estradiol were 67, 53, 48 and 39, respectively. Detection by spraying with 5 % phosphomolybdate reagent and heating at 80 ºC until the zones were detected. Identification of the four estrogens by comparison with the standards. The method is selective, sensitive, reliable, accurate, robust, and suitable for rapid screening of illegal estrogenic hormones in TCM preparations.